It has been common practice for decades to rely merely on visual inspection of the condition of a tire to determine when the pressure becomes too low. Sometimes, the conclusion drawn from the visual inspection has been erroneous. Other times, the driver or the filling station attendant forgets to check the tire condition.
The result of these erroneous conclusions or check failures has led to riding on improperly inflated tires, which greatly increases wear and makes the vehicle not as responsive, under emergency conditions, as with properly inflated tires.
In recent years, pressure signal attachments have been devised which are mountable on valve stems of tires to signal when the tire pressure is too low. However, again, forgetfulness to check, leads to the same problems as above described. In addition, there are different pressure requirements for the front and rear wheels of a vehicle, between large tires and small ones, between tires on heavy vehicles versus light ones, etc. This has required the availability of different attachments for different circumstances.